Fig. 2.

Selective and tunable adsorption of MPPs on copolymer film. a, b, d, e, g, h Dynamic adsorption curves of various PPs (1pS–4pS) and NMPs adsorbed on the PNI-co-ATBA_0.2 film, measured by QCM. a, b Peptide solutions with consistent pH of 7.4 and temperature of 20 °C, but different solvent polarities: (a) CH₃CN/H₂O v v⁻¹ = 4:1 or (b) CH₃CN/H₂O v v⁻¹ = 1:1. d, e Consistent solvent polarity of CH₃CN/H₂O v v⁻¹ = 4:1 and temperature of 20 °C, but different solution pH conditions: (d) pH: 5.2 or (e) pH: 9.5. g, h Consistent solvent polarity of CH₃CN/H₂O v v⁻¹ = 4:1 and pH of 7.4, but different temperatures: (g) 10 °C or (h) 30 °C. c, f, i CH₃CN proportion- (c), pH- (f) or temperature (i)-dependent QCM resonator frequency change (ΔF) in response to the adsorption of 4pS on PNI-co-ATBA_0.2 (black), poly(ATBA) (red) or ATBA monolayer (blue) surface, respectively. j Dynamic adsorption curves of tyrosine-modified PPs with mono-, di- or tri-phosphates (1pY–3pY) adsorbed on the PNI-co-ATBA_0.2 film in CH₃CN/H₂O (v v⁻¹ = 4:1) at pH 7.4 and 20 °C. k Adsorption curves of serine- (black), threonine- (red) or tyrosine- (blue) modified tri-PPs (3pS, 3pT and 3pY) adsorbed on the PNI-co-ATBA_0.2 film in CH₃CN/H₂O (v v⁻¹ = 4:1) at pH 7.4 and 20 °C. l Peptide sequences of NMPs and various PPs tested in this study. The phosphate-modified amino acids are indicated by red characters and their corresponding chemical structures